Aircraft are being designed to use electrical power more, and various other sources of power, such as hydraulic and pneumatic sources, less. Aircraft system architectures that rely either solely, or in greater abundance, upon electrical power are sometimes referred to as More Electric Architecture (MEA) systems. Typically, MEA systems use starter-generators to both start the aircraft main engines and supply electrical power to various system loads. These various system loads may utilize electrical power at various frequencies and voltages. Thus, many MEA systems, and/or the starter-generators that are currently used to power MEA systems, typically include relatively complex and heavy power electronics circuits. For example, some systems may include inverters, for converting DC to AC power, rectifiers, for converting AC power to DC power, and potentially complex voltage and frequency control circuits, which can increase overall complexity, cost, and maintenance.
Although brush-type DC machines may alleviate the need for some of these complex and heavy electronic circuits, these also suffer certain drawbacks. For example, the brushes tend to wear fairly quickly, which can reduce machine reliability and increase the need for periodic maintenance and cleaning. Some brush-type DC machines can also suffer what is known as torque ripple during startup. In some instances, the torque ripple can be large, which can result in poor starter performance.
Hence, there is a need for a generator that can be used to supply various loads and does not rely on relatively complex and heavy inverters and frequency control circuits for proper operation, and/or does not suffer reduced reliability from brush wear, and/or the need for potentially frequent maintenance and cleaning, and/or does not experience significant torque ripple during startup. The present invention addresses one or more of these needs.